A silder crank mechanism is shown in fig: Let the crank OB makes an angle θ with the inner dead centre (IDC) and rotates in a clockwise direction about the fixed point O with uniform angular velocity ωBO rad/s.
∴ Velocity of B with respect to O or velocity of B,
vBO = vB x ωBO OB, acting tangentially at B.
We know that centripetal or radial acceleration of B with respect to O or acceleration of B,
arBO = aB = ω2BO x OB = v2BO/OB